The purpose of this project is to participate in large scale, multi-institutional, cooperative trials planned to increase the understanding and curability of all the common childhood malignancies. A major proposal is the investigation of the effectiveness of combining intensive chemotherapy with radiotherapy in the initial treatment of acute lymphoblastic and undifferentiated leukemia of childhood. Further proposals include Phase I and II studies of newly developed chemotherapeutic agents as well as immunotherapeutic proposals and Phase III studies to determine the most beneficial treatment of Ewing's sarcoma, Wilm's tumor, neuroblastoma, osteogenic sarcoma, and myelogenous leukemia.